Hydrodynamic behavior measurement methods

Current tests are generally destructive (i.e., sample is altered or destroyed) and robust estimates of measurement system variability (all aspects of the procedure including the operators) are difficult to obtain without using methods such as Gauge R R-reproducibility and repeatability (14). Suitability of current methods then is based on calibration using a calibrator system that has its own built-in variability and other assumptions (e.g., in physical testing such characteristics as size, shape, density can alter aerodynamic and/or hydrodynamic behavior of materials in a test system and contribute to systems variability). 

Both qualitative and quantitative insight can be garnered from transient X -i, i-t and r -t measurements in quiescent or stirred solutions, while measurements of steady-state behavior are best performed under well-defined hydrodynamic conditions. Typically, a rotating disc electrode (RDE), or a related method, is used to specify and/or modulate the hydrodynamic boundary layer thickness, 8. With an RDE the boundary layer is specified by... 

It is evident from the above discussion that the free volume data derived from positron lifetime measurements is incapable of providing information on the composition-dependent miscibility level of the blend. At this point, a new method based on the same free volume data measured from positron lifetime measurements was introduced to determine the miscibility of binary blends. The new method was based on hydrodynamic interactions (the mathematics required have been explained in detail earlier), and calculations of the y parameter derived from the hydrodynamic interaction approach were made for three selected polymer blends, namely poly(styrene-co-acrylonitrile) (SAN)/poly(methyl methacrylate) (PMMA) (completely miscible), poly(vinyl chloride) (PVC)/poly(methyl methacrylate) (PMMA) (partially miscible) and poly(vinylchloride) (PVC)/polystyrene (PS) (immiscible) (see Figure 27.13). As can be seen, this parameter behaves similar to the interchain interaction parameter /3, in the sense that it exhibits a complex behavior making it difficult to determine the composition-dependent miscibility of the blends. 

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